var tab1 = document.getElementById('Introduction'),
    tab2 = document.getElementById('Unsettled'),
    tab3 = document.getElementById('Settled'),
    c1 = document.getElementById('Introducts'),
    c2 = document.getElementById('Unset');
    c3 = document.getElementById('Set');
function changeTab1() {
    tab1.className = 'YR xx';
    tab2.className = 'WJS';
    tab3.className = 'YJS';
    c1.className = 'selected list_content '
    c2.className = 'list_content_1';
    c3.className = 'list_content_2';
}
function changeTab2() {
    tab1.className = 'YR';
    tab2.className = 'WJS xx';
    tab3.className = 'YJS';
    c1.className = 'list_content'
    c2.className = 'selected list_content_1 ';
    c3.className = 'list_content_2';
}
function changeTab3() {
    tab1.className = 'YR';
    tab2.className = 'WJS';
    tab3.className = 'YJS xx';
    c1.className = 'list_content'
    c2.className = 'list_content_1';
    c3.className = 'selected list_content_2 ';
}